With these kinds of drilling devices, which may also comprise an impact drive unit and/or a vibration drive unit apart from the drive unit for advance and rotation, the rod assembly is used for the transmission of pushing forces and torque onto the drilling tool as well as for the transmission of pulling forces when taking out the rod assembly out of a drilling hole against the drilling direction, as normally done. Furthermore drilling rod assemblies for wet drilling are used to transport drilling fluid in direction of the drilling tool e.g. for the hydraulic mining of the soil. Drilling rod assemblies thus are subject to large static and dynamic load and thus require connections for the single pipe sections, which can cope with these loads and are, if necessary, liquid tight.
In practical use screwed connections are normally used as rod connections. These do however make time consuming screwing processes, often with use of special rod screwing devices, necessary on the one hand and are especially extremely sensitive to soiling and mechanical damage. Additionally, screwed drilling rod assemblies allow only one direction of rotation during drilling, as unscrewing of the connection would result otherwise. Even if the time effort for applying the screwing device, the actual screwing and the withdrawal of the screwing device per rod section is small, the related stop periods add up substantially with increasing rod assembly or drilling length.